/Engine/Source/Editor/Sequencer/Public/MVVM/Selection/Selection.h
Main key selection class that stores selected key handles, and the channel they originated from
struct FKeySelection : public [UE::Sequencer::TUniqueFragmentSelectionSet< FKeyHandle, FChannelModel >](API\Editor\SequencerCore\MVVM\Selection\TUniqueFragmentSelectionSet)